title: Self-assembly based plasmonic arrays tuned by atomic layer deposition for extreme visible light absorption.
abstract: Achieving complete absorption of visible light with a minimal amount of material is highly desirable for many applications, including solar energy conversion to fuel and electricity, where benefits in conversion efficiency and economy can be obtained. On a fundamental level, it is of great interest to explore whether the ultimate limits in light absorption per unit volume can be achieved by capitalizing on the advances in metamaterial science and nanosynthesis. Here, we combine block copolymer lithography and atomic layer deposition to tune the effective optical properties of a plasmonic array at the atomic scale. Critical coupling to the resulting nanocomposite layer is accomplished through guidance by a simple analytical model and measurements by spectroscopic ellipsometry. Thereby, a maximized absorption of light exceeding 99% is accomplished, of which up to about 93% occurs in a volume-equivalent thickness of gold of only 1.6 nm. This corresponds to a record effective absorption coefficient of 1.7 × 10(7) cm(-1) in the visible region, far exceeding those of solid metals, graphene, dye monolayers, and thin film solar cell materials. It is more than a factor of 2 higher than that previously obtained using a critically coupled dye J-aggregate, with a peak width exceeding the latter by 1 order of magnitude. These results thereby substantially push the limits for light harvesting in ultrathin, nanoengineered systems.
authors.affiliation: Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Carl
authors.initials: C
authors.lastname: Hägglund
authors.forename: Gabriel
authors.initials: G
authors.lastname: Zeltzer
authors.forename: Ricardo
authors.initials: R
authors.lastname: Ruiz
authors.forename: Isabell
authors.initials: I
authors.lastname: Thomann
authors.forename: Han-Bo-Ram
authors.initials: HB
authors.lastname: Lee
authors.forename: Mark L
authors.initials: ML
authors.lastname: Brongersma
authors.forename: Stacey F
authors.initials: SF
authors.lastname: Bent
mesh_terms: D000042:Absorption; D003198:Computer Simulation; D017076:Computer-Aided Design; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D008962:Models, Theoretical; D012542:Scattering, Radiation; D020349:Surface Plasmon Resonance / Q000295:instrumentation* / Q000379:methods*